The present invention relates to a hollow charge of a directed explosion effect as well as a method for the manufacture of the metallic cone of the hollow charge.
The subject of the present invention is a hollow charge of a directed explosion effect. The charge comprises a mantle of the charge portion, an explosive material fitted inside the mantle, a detonator fitted at one end of the charge, and a metal cone fitted at the opposite end of the charge, the mantle of the charge and the metal cone being precisely centered on a common symmetry axis, on which the detonator is also positioned.
In the prior art, blocked mine shafts are opened by means of explosives, whereby the explosive material is placed as close to the vault formation as possible, or into the vault formation. It is a commonly occurring drawback that the positioning of the explosive close to the vault formation is difficult and dangerous, and that the power effect of the explosive may not achieve the desired result. The object of the present invention is to provide a considerable improvement in the opening of blocked or vaulted mine shafts by means of a hollow charge or mine charge in accordance with the invention, which charge is placed underneath the vault formation and directed towards the vault formation. The hollow charge in accordance with the invention may be detonated from a distant location, so that it is remote-operated.
The hollow charge in accordance with the invention is mainly characterized in that, as viewed from the direction of the object to be blasted, the shape of the cone, made of pure copper, of the hollow charge is in such a way differential that the convexity of the wall of the cone, whose thickness is uniform within the area of the entire cone, from the wall of a straight cone of equal cone angle is less than the thickness of the wall of the copper cone, preferably about one half of the said thickness of the wall, and that the point of the copper cone is preferably a part of a concave globe face, whereby, owing to the shape of the copper cone, when the hollow charge is being exploded, the differences in acceleration of the parts of its mass are as close to zero as is possible in practice.
In the hollow charges in use at present, only the point mass, the jet, is utilized, so that the mass chunk following behind, whose speed is 200 to 300 m/s, is not utilized. In the hollow charge or mine charge in accordance with the present invention, the jet and the chunk--i.e. the whole mass--travel at almost the same speed, as compared with each other, at about 2500 to 3000 m/s, while the detonating rate of the explosive is 7000 to 8000 m/s. This of course has entirely novel power effects. The copper cone of the hollow charge in accordance with the invention is specifically shaped so that the differences in acceleration between the parts of the mass are as close to zero as is possible in practice. The hollow charge operates by means of the spherical-front principle.